1. Field of the Invention
The present invention relates to route optimization between mobile routers of a mobile network, for example a mobile IP network (NEMO) or an Internet Protocol (IP) based mobile ad hoc network (MANET), and a correspondent node.
2. Description of the Related Art
Proposals have been made by Internet Engineering Task Force (IETF) groups for improved mobility support of Internet Protocol (IP) based mobile devices (e.g., laptops, IP phones, personal digital assistants, etc.) in an effort to provide continuous Internet Protocol (IP) based connectivity. The IETF has two working groups focusing on mobile networks, a Mobile Ad-hoc Networks (MANET) Working Group that is working to develop standardized MANET routing specification(s) for adoption by the IETF, and NEMO (mobile networks). NEMO uses Mobile IP (MIP) to provide connectivity between mobile networks and the infrastructure (e.g., the Internet). The key component in NEMO is a mobile router that handles MIP on behalf of the mobile networks that it serves.
According to the MANET Working Group, the “mobile ad hoc network” (MANET) is an autonomous system of mobile nodes connected by wireless or wired links—the union of which form an arbitrary graph. The nodes are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet.
A “Mobile IPv6” protocol is disclosed in an Internet Draft by Johnson et al., entitled “Mobility Support in IPv6”, available on the World Wide Web at the address: http://www.ietf.org/internet-drafts/draft-ietf-mobileip-ipv6-20.txt (the disclosure of which is incorporated in its entirety herein by reference). According to Johnson et al., the Mobile IPv6 protocol enables a mobile network host to move from one link to another without changing the mobile network host's IP address. Hence, a mobile network host is always addressable by its “home address”, an IP address assigned to the mobile network host within its home subnet prefix on its home link. Packets may be routed to the mobile network host using this address regardless of the mobile network host's current point of attachment to the Internet. The mobile network host may also continue to communicate with other hosts (stationary or mobile) after moving to a new link. The movement of a mobile network host away from its home link is thus transparent to transport and higher-layer protocols and applications.
In addition, Johnson et al. assumes that use of Mobile JPv6 eliminates the need to deploy special routers as “foreign agents” as are used in Mobile TPv4. In Mobile IPv6, mobile network hosts make use of IPv6 features, to operate in any location without any special support required from the local router.
Existing Internet Drafts for NEMO do not optimize the path to an arbitrary correspondent node (CN), let alone providing a secure, optimized path. One proposal for route optimization is provided by the Internet Draft by Ohnishi et al., entitled “Mobile IP Border Gateway (MBG)”, available on the World Wide Web at the address: http://www.ietf.org/internet-drafts/draft-ohnishi-mobileip-mbg-00.txt as well as the World Wide Web address http://www.mobile-ip.de/ftp/pub/ietf/drafts/draft-ohnishi-mobileip-mbg-00.txt (the disclosure of which is incorporated in its entirety herein by reference). As recognized by Ohnishi et al., the current Mobile IP specification forces all packets forwarded to a mobile node (MN) from a correspondent node (CN) to be routed via that mobile node's home agent: this routing via the home agent often leads to triangular routing, which in turn causes data transmission delay and wastes network resources.
However, the MBG proposed by Ohnishi et al. is limited to optimizing routes within the internal network of an Internet Service Provider (ISP). Hence, relatively inefficient triangular routing may still become prevalent between a mobile node and the correspondent node in cases where the MN or the CN are outside a prescribed ISP.